Method for making briquettes containing coal



Mam}! 1967 V P. SCHMALFELD ETAL 3,303,219

METHOD FOR MAKING BRIQUETTES CONTAINING COAL Filed May 18, 1964 2 Sheets-Sheet 1 1967 P. SCHMALFELD ETAL 3,308,219

METHOD FOR MAKING BRIQUETTES CONTAINING COAL Filed May 18, 1964 2 Sheets-Sheet 2 United States Patent Main, Germany Filed May 18, 1964, Ser. No. 367,961 Claims priority, application Gzrmany, May 16, 1963,

M 5 Claims. (Cl. 264-122) This invention relates to a method of briquetting a material such as coal, coke, ore or mixtures thereof with a caking coal.

It has been proposed to briquette fine-grained caking coals by heating them to temperatures at which they soften or become plastic, and then briquctting them in double cylinder or plunger presses at pressures of from about 300 to 1,000 atmospheres. Many coals which have a strong softening property cannot be briquetted alone, because the pressed material agglomerates when heated. Nevertheless, it is desired to utilize the good caking property of such coals by admixing them as binding agents with fine-grained substances which are required to be briquetted, for example, non-caking coals, cokes, ores and smelting additives. -It has been proposed to heat nonsoftening coal or coke to a temperature above the softening range of caking coals and then to mix it with a dry caking coal which has been preheated below its softening temperature, in such proportions that the desired temperature in the softening range of the caking coals is achieved in the mixture, and to briquet this mixture.

The manufacture of such briquettable mixtures from a caking coal and non-caking constituents such as coke, coal, fine ore and the like, presents many apparatus difficulties.

It has been proposed to heat coke as a non-caking constituent suspended in a gas stream and to introduce a finegrained caking coal into the gas stream, whereupon the solids are separated from the gas stream so that the coke and coal are discharged as a common mixture.

Types of mechanical mixing units known for the manufacture of briquctting material containing a binding agent consists of containers either having a stirring unit rotating about a vertical axis, or troughs in which one or a plurality of paddle shafts rotate about horizontal axes. But these mixing elements do not operate in a reliable manner, because they do not mix the material uniformly, nor sufficiently rapidly. Agglomeration and lump formation also frequently occur in the mixture, and even cause jamming of the apparatus.

A method of degassing fine-grained caking coal by admixture of fine-grained hot heat carriers has been proposed, wherein a hot heat carrier and the coal is passed in regulated quantities through a screw-type mixer, degassing of the coal with preservation of its grain fineness being achieved with continuous movement and intensive mixing of the heat carrier and coal.

A mixer suitable for performing that method contains in a housing two mixing shafts rotatable in the same direction, the profiles of which are preferably constructed as bodies of lenticular cross-section. These mixing bodies mutually sweep one another at every point of their surface with a specific small clearance, and also sweep the wall of the mixing chamber, so that no agglomeration can occur. The rotary mixing bodies also intensively circulate the material to be mixed, in that they forward it from one shaft to the other and continuously move it at a constant speed.

It has been found that such mixing units are well suited for the preparation of a briquctting material which contains caking coals or coal having pronounced softening propertites in the plastic state.

According to the present invention, there is provided a method of briquctting a material such as coal, coke, ore or mixtures thereof with a caking coal wherein the nonplasticizable fraction of the material to be briquetted is superheated to a temperature above the temperature at which the caking coal attains a plastic condition, and is then combined with the caking coal to form a mixture in which the temperature lies in the range where the caking coal is in a plastic condition, the superheated nonplasticizable fraction of the mixture and the caking coal being introduced in common into a mixing unit having two mixing elements with lenticular profiles mounted in shafts rotating in the same direction, and in which the materials are first mixed with partial degassing of the caking coal to a uniform mixture having a temperature in the range where the caking coal is in a plastic condition, cooling the mixture by at least 20 C. by injection of water, and then briquctting at said cooled temperature in a briquctting press.

The plasticity range of the caking coal is dependent upon the character of the coal and customarily lies between 350 C. and 480 C., more usually between 380 C. and 450 C.

The quantitative proportion and the temperature of the caking coal and of the nonplasticizable fraction of the briquetting material are so adjusted at entry into the mixing unit that the mixture approximately attains a temperature at the plasticity maximum of the caking coal, or slightly higher. The temperature position of the plasticity maximum is a specific property of every coal, but also depends upon the speed with which this temperature is attained. The absolute value of this maximum increases with the speed of heating.

A rapid temperature equalization occurs during the rapid and thorough intermixing of the constituents at different temperatures, and the caking coal acquires a correspondingly high plasticity owing to the large gain in heat. A partial degassing and also detarring occurs simultaneously. The resultant volatile products are removed from the housing of the mixer.

The subsequent cooling by the evaporation of the injected water freezes, as it were, the decomposition state of the caking coal is the plasticity range. The development of gas and tar ceases, and the caking coal is virtually degassed with reference to the temperature arrived at during cooling. This is important, because any development of gas in the subsequent pressing process is thereby inhibited. The caking property and binding capacity of the coal, which are related to the softening property, are largely preserved after cooling if the cooling takes place rapidly and uniformly, as in the case when using a mixing unit with mixing elements having lenticular profiles.

The mixing and the heating of the coal up to the condition of plasticity and degassing and the subsequent cooling may take place in mutually consecutive sections of the mixing unit, but may also be performed in two separate series-connected mixing units.

An intermediate bin is conveniently disposed between the mixer unit or mixer units and the briquctting press, and is thermally insulated. A specific reserve of ready briquctting material is maintained in this intermediate bin and acts as a gas barrier between the mixing unit and the briquctting press; it also permits uniform feeding of the press by means of known valves, chutes, screw conveyors and the like.

Consequently the press chamber remains free of carbonization gases. It is, however, convenient to encapsulate the press to a considerable degree and possibly to maintain it in an inert gas.

The invention is more fully described with reference 3 to the accompanying drawings, which illustrate diagrammatically and by 'way of example an embodiment thereof, and in which:

FIGURE 1 is a flow diagram of a plant for forming briquettes of coal;

FIGURE 2 is a vertical axial section through a mixing unit of the plant; and

FIGURE 3 is a section taken along the line AA, FIGURE 2.

Referring now to the drawings, the plant comprises mixing units 1 and 5, an intermediate bin 8 and a briquetting press 10.

The nonplasticizable fraction of the briquetting material, for example, coke, having been superheated with reference to the mixture temperature, is fed to the input side of the mixing unit 1 through a pipe 2, and the caking coal, which may have been preheated, is similarly fed through a pipe 3, the two possibly being fed in at a short distance from one another. The two material streams are controlled in a mixture ratio given by the properties of the initial materials, that is, of the caking coal and of the coke. The temperatures of the coke and of the coal are adjusted so that the mixture attains a temperature which is close to the maximum of the plasticity of the caking coal.

The volatile constituents, tar and gas, which leave the mixture, are removed from the housing of the first mixer through a pipe 12.

In this condition, the mixture is passed through a pipe 4 into the mixing unit 5, where cooling is brought about by spraying in water through a pipe 6, the water evaporating and thus cooling the hot mixture. The cooled mixture passes through a connecting pipe 7 to the inermediate bin 8, and is passed from the latter through apportioning devices 9 to the press channel of the briquetting press 10. The briquettes are discharged through chute 11.

A temperature measuring device 13 may be disposed in advance of the water input pipe in the direction towards the pipe 4, being adjusted to the temperature of maximum plasticity of the caking coal. The temperature of the hot coke at the pipe 2 is controlled according to the said temperature.

The mixers 1 and illustrated in FIGURE 1 may be combined to form a single mixing unit of suitable length. In that case, the water input pipe is conveniently located approximately in the center of the mixing path.

FIGURES 2 and 3 show a mixing unit in greater detail.

Housing 26 of the mixer is clad with a heat-insulating masonry wall 27. In the housing, lenticular shaped mixing elements 23 rotate in the same direction about their shafts 21 and 22, said shafts being journalled at the end faces of the housing and driven in a suitable manner, not shown.

The constituents required to be mixed, namely hot coke and caking coal, are introduced in a determined quantitative ratio through shafts 24 and 24a, respectively, which may also be combined as one shaft. The mixture is discharged through a shaft 28 and fed to a further mixer or to the intermediate bin in advance of the briquetting press. Volatile constituents produced during mixing are discharged through a pipe 25. If the plant is operated with two series-connected mixing units as shown in FIG- URE 1, then the water for cooling the mixture is introduced through the pipe 6 (FIGURE 1).

If the mixer illustrated in FIGURE 2 is used for mixing and cooling, then the addition of the water occurs through a pipe 30. The steam formed from the water passes off through the discharge pipe 25 together with the volatile constituents of the coal.

The invention is further illustrated by the following examples which give some specific operating conditions:

EXAMPLE 1 Hard coke having a grain size of 0 to 3 mm., after being heated to 500 C., is introduced into the mixer unit together with caking coal having a grain size of O to 2 mm., which has been preheated to 250 C., in the ratio of 70:30 by weight. In the mixer unit, carbonization gases are developed and a mixing temperature of 425 C. at which the caking coal is plastic is rapidly attained. In this condition, the mixture is fed to a second mixing unit and is there cooled to 370 C. by evaporation of injected water so that no further gases or tar vapors are produced. The cooled mixed material is then charged by way of a small intermediate bin into a double cylinder press and is pressed into ovoid briquettes which contain 1.2% weight residual tar and 10.0% Weight volatile constituents.

EXAMPLE 2 Hard coke having a grain size of 0 to 3 mm. is heated to 560 C. and is fed, together with good caking and weakly swelling bituminous coal, which has been preheated to 100 C. and dried, in proportions by weight of :25, is fed to a mixing unit, where a temperature equalization to 440 C. rapidly takes place. After cooling the mixed material in the second half of the mixer unit to 360 C. by evaporation of injected water, the strong gas development which initially occurred ceases, so that the mixed. material can be pressed to firm briquettes. The finished briquettes contain 0.8% weight carbonization tar and 7.0% weight volatile constituents.

EXAMPLE 3 Anthracite having a grain size of 0 to 4 mm. is heated to 580 C. and then fed, together with a good caking and weakly swelling coal, which has been preheated to 200 C., in the proportions by weight of 65:35, to a mixer unit, where a mixing temperature of 400 C. is very rapidly attained with strong development of gas. The mixed material, which is plastic at this temperature, is cooled to 350 C. in a second mixing unit by injection of water and is then pressed into briquettes. The latter contain 1.5% weight carbonization tar and 10.0% weight volatile constituents.

EXAMPLE 4 Iron ore having a grain size of 0 to 3 mm. is heated to 600 C. and is introduced, together with a good caking coal having a grain size of 0 to 2 mm. which has been preheated to 150 C., in the proportion by weight of 70:30, into a mixing unit. A mixing temperature of 450 C. is attained in the mixing unit in a short time, and the mixture becomes plastic. By evaporating injected water in the second half of the mixing unit, the mixed material is cooled to 400 C., whereby the gas development is terminated. The mixed material is then pressed in an extruder press to form briquettes which contain 0.5% weight carbonization tar and 5.0% weight volatile constituents.

Having noW described the means by which the objects of the invention are obtained:

We claim:

1. A method of briquetting a nonplasticizable material such as coal, coke, ore or mixtures thereof with a caking coal which is plastic at a temperature range of from about 350 to 480 C. comprising heating the nonplasticizable material to be briquetted to a temperature above the temperature at which the caking coal attains a plastic condition, mixing both the heated non-plasticizable material and the caking coal by forwarding them at a constant speed through a mixing device, a partially degassing the cake coal by direct heat exchange with the hot nonplasticizable material during the first part of the mixing where the caking coal is brought into plastic condition, injecting cooling fiuid into the mixture during the last part of the mixing to lower the mixing temperature by about 20 to C., and then briquetting the mixture at the cooled temperature in a briquetting press.

2. A method as claimed in claim 1, further comprising preheating the caking coal before admixture with the nonplasticizable material.

3. A method as in claim 2, comprising cooling the mixture by about 20 to 50 C.

4. A method as in claim 3, comprising cooling said mixture by spraying in steam.

5. In the method of claim 1, further comprising mixing the nonplasticizable material and the coal in two steps, and injecting said cooling fluid into the beginning of the second step which is the last part of the mixing.

References Cited by the Examiner UNITED STATES PATENTS Curtis et a1 754 Brisse et a1. 753

Rueckl 753 Kardaun et a1. 264122 BENJAMIN HENKIN, Primary Examiner. 

1. A METHOD OF BRIQUETTING A NONPLASTICIZABLE MATERIAL SUCH AS COAL, COKE, ORE OR MIXTURES THEREOF WITH A CAKING COAL WHICH IS PLASTIC AT A TEMPERATURE RANGE OF FROM ABOUT 350 TO 480*C. COMPRISING HEATING THE NONPLASTICIZABLE MATERIAL TO BE BRIQUETTED TO A TEMPERATURE ABOVE THE TEMPERATURE AT WHICH THE CAKING COAL ATTAINS A PLASTIC CONDITION, MIXING BOTH THE HEATED NON-PLASTICZABLE MATERIAL AND THE CAKING COAL BY FORWARDING THEM AT A CONSTANT SPEED THROUGH A MIXING DEVICE, A PARTIALLY DEGASSING THE CAKE COAL BY DIRECT HEAT EXCHANGE WITH THE HOT NONPLASTICIZABLE MATERIAL DURING THE FIRST PART OF THE MIXING WHERE THE CAKING COAL IS BROUGHT INTO PLASTIC CONDITION, INJECTING COOLING FLUID INTO THE MIXTURE DURING THE LAST PART OF THE MIXING TO LOWER THE MIXING TEMPERATURE BY ABOUT 20 TO 100*C., AND THEN BRIQUETTING THE MIXTURE AT THE COOLED TEMPERATURE IN A BRIQUETTING PRESS. 